This invention relates to an air filter for internal combustion engines comprising a housing with a clean air outlet and an unfiltered air inlet provided with a screen, and a filter insert in the housing.
Air filters for internal combustion engines of motor vehicles usually have an inlet for unfiltered air arranged in an area to which cold air can flow unhindered. The air inlet is therefore normally situated behind the radiator grill of the vehicle or in the vicinity of a fender. It has been found, particularly in countries where snow is abundant, that during drives which are confronted by heavy snowfall or blowing snow, snow is aspirated together with the unfiltered air into the air filter, and this entrained snow accumulates on the filter insert and may clog the filter. Such clogging may even become sufficiently severe to stop the engine.
Another disadvantage of entrained snow is that when the engine is turned off, the snow accumulated on the air filter insert may start to melt and then refreeze to form a layer of ice which interrupts the air supply to the engine and therefore prevents the engine from starting.